The present invention relates to a composition for preventing, improving or treating a mental disorder, the composition containing asp. bacteria-derived vesicle as an active ingredient. The present inventors have confirmed that, when asp. bacteria-derived vesicle is administered to a stress and depression animal model, resistance to stress efficiently increases, and an effect of treating chronically persisting long-term depression behavior is exhibited, and thus thesp. bacteria-derived vesicle, according to the present invention, is expected to be capable of being usefully employed in developing a medicine or a functional health food, etc., for preventing, reducing the symptoms of or treating a mental disorder such as stress, anxiety disorder, post-traumatic stress disorder, panic disorder, depression, autism spectrum disorder, attention deficit hyperactivity disorder and schizophrenia.
